If you use a script-driven platform for your site, it stores its information inside a database and the more substantial the site becomes, the more information it collects. For instance, if you start an e-store, the size of the database the e-commerce script employs will increase whenever you add more products. The exact same is valid for a forum script - the more users which register and the more opinions they submit, the larger the database. If your sites gain popularity or you simply want to add more content, this might develop into a problem in case that your hosting account has limited database storage space. The particular effect of hitting the limit shall be depends on the script - the website may function correctly, but you may not be able to include any new info; the site can be viewed with errors; or, in the worst case scenario, the entire internet site might go offline.